q.Lock

Acquire a lock and register a deferred Unlock in one statement. Statement-only.

Signature

func Lock(l sync.Locker)

Accepts any sync.Locker — *sync.Mutex, *sync.RWMutex (write side), rwm.RLocker() (read side), or a user-defined type with Lock() / Unlock().

What q.Lock does

func (s *Store) Set(k, v string) {
    q.Lock(&s.mu)
    s.data[k] = v
}

rewrites to:

func (s *Store) Set(k, v string) {
    _qLock1 := &s.mu
    _qLock1.Lock()
    defer _qLock1.Unlock()
    s.data[k] = v
}

The locker expression is evaluated exactly once and bound to a local — important when you pass something like rwm.RLocker() (each call returns a fresh Locker):

q.Lock(s.rwm.RLocker())   // read side — binds once, Locks once, defers matching Unlock

Statement forms

q.Lock returns nothing, so it's always a plain expression statement. Using it as a value (v := q.Lock(...)) is a Go type error caught by the compiler.

See also

• q.Open — the general (T, error) + defer cleanup pattern; q.Lock is a specialisation of it for lockers with no error return.